1. Field of the Invention
The present invention relates to amino acid complexes of the formula I,where the variables are defined as follows:     M is selected from among Fe, Co, Ni, Pd, Pt and Ir,    X is selected from among O and S;    R1 and R2 are identical or different and are each selected from among            hydrogen,        C1-C8-alkyl, substituted or unsubstituted,        C3-C12-cycloalkyl, substituted or unsubstituted,        C7-C13-aralkyl,        C6-C14-aryl, unsubstituted or substituted by one or more identical or different substituents selected from among        C1-C8-alkyl, substituted or unsubstituted,        C3-C12-cycloalkyl,        C7-C13-aralkyl,        C6-C14-aryl,        halogen,        C1-C6-alkoxy,        C6-C14-aryloxy,        SiR4R5R6 and O—SiR4R5R6, where R4-R6 are selected from among C1-C8-alkyl, C3-C12-cycloalkyl, C7-C13-aralkyl and C6-C14-aryl;        five- to six-membered nitrogen-containing heteroaryl radicals Y, unsubstituted or substituted by one or more identical or different substituents selected from among        C1-C8-alkyl, substituted or unsubstituted,        C3-C12-cycloalkyl,        C7-C13-aralkyl,        C6-C14-aryl,        halogen,        C1-C6-alkoxy,        C6-C14-aryloxy,        SiR4R5R6 and O—SiR4R5R6, where R4-R6 are selected from among C1-C8-alkyl, C3-C12-cycloalkyl, C7-C13-aralkyl and C6-C14-aryl,        and CH2—Y, where Y is as defined above;            y is an integer from 0 to 4;    L1 is an uncharged, inorganic or organic ligand;    L2 is an inorganic or organic anionic ligand, where L1 and L2 may be joined to one another by one or more covalent bonds;    z is an integer from 0 to 3;    x is an integer from 0 to 3.
Furthermore, the present invention relates to a process for preparing the novel amino acid complexes of the formula I and to catalyst systems for the polymerization or copolymerization of olefins, comprising one or more amino acid complexes of the formula I and, if desired, an activator, and also to a process for the polymerization or copolymerization of olefins using the catalyst system of the present invention.
2. Description of the Background
Polymers and copolymers of olefins are of great economic importance because the monomers are readily available in large quantities and because the polymers can be varied within a wide range by variation of the production process or the processing parameters. In the production process, particular attention has to be paid to the catalyst used.
The systems described in the literature are not free of disadvantages. Thus, the cyclopentadienyl ligands of most metallocenes require complicated syntheses which can take 4 or more hours, for example as described in H.-H. Brintzinger et al., Angew. Chem. 1995, 107, 1255, in EP-A 0 549 900 or EP-A 0 576 970. However, multistage syntheses make the catalysts more expensive.
The systems disclosed in WO 96/23010 give, after activation with methylaluminoxane (“MAO”), highly branched polymers which, however, do not have a sufficiently high molecular weight for numerous materials applications.
The complexes described by Brookhart and Gibson (e.g. WO 98/27124) are simple to obtain in terms of the synthesis, but they only incorporate comonomers in very small amounts. The polymerization of ethylene, for example, gives highly linear, brittle polymers having a limited suitability as materials. K. Severin et al., Chem. Ber. 1995, 128, 1127, disclose Rh complexes of the formula A where R=methyl or benzyl, which can readily be synthesized from the natural amino acids. They are suitable as chiral catalysts for hydrogenation, as cytostatics or as labeling reagents in biochemistry. However, they are unsuitable as polymerization catalysts.